We report the synthesis and characterization of the antimony-doped oxypnictide superconductor, LaO0.8F0.2FeAs 1-xSbx (x = 0.05 and 0.10). The parent compound LaOFeAs with fluorine doping exhibits superconductivity at the maximum transition temperature ∼28.5K (at ambient pressure). Here we partially substitute As by Sb (LaO0.8F0.2FeAs1-xSbx) and observe enhancement of the transition temperature to 30.1K. This is one rare case where Tc increases with doping in the conducting layer (FeAs) and this leads to the highest transition temperature in any La-based oxypnictide. X-ray diffraction and energy-dispersive x-ray analysis measurements confirm the phase purity of the samples and the presence of Sb. The magneto-resistance measurements show that the value of the upper critical field Hc2(0) is about 73T, corresponding to a coherence length (ξGL) of 22. The Seebeck coefficient measurements indicate electron transport with a strong contribution from electron-electron correlation. These results provide interesting insight into the origin of superconductivity in this novel series of compounds. © 2009 IOP Publishing Ltd.